[Contribution of 18-F-FDG PET for detection of head and neck carcinomas with an unknown primary tumor]

Role of fluorine-18 fluorodeoxyglucose PET/CT in head and neck oncology: the point of view of the radiation oncologist

Squamous cell carcinoma is the most common malignant tumour of the head and neck. The initial TNM staging, the evaluation of the tumour response during treatment, and the long-term surveillance are crucial moments in the approach to head and neck squamous cell carcinoma (HNSCC). Thus, at each of these moments, the choice of the best diagnostic tool providing the more precise and larger information is crucial. Positron emission tomography with fluorine-18 fludeoxyglucose integrated with CT (¹⁸F-FDG-PET/CT) rapidly gained clinical acceptance, and it has become an important imaging tool in routine clinical oncology. However, controversial data are currently available, for example, on the role of ¹⁸F-FDG-PET/CT imaging during radiotherapy planning, the prognostic value or its real clinical impact on treatment decisions. In this article, the role of ¹⁸F-FDG-PET/CT imaging in HNSCC during pre-treatment staging, radiotherapy planning, treatment response assessment, prognosis and follow-up is reviewed focusing on current evidence and controversial issues. A proposal on how to integrate ¹⁸F-FDG-PET/CT in daily clinical practice is also described.

Detecting Residual/Recurrent Head Neck Squamous Cell Carcinomas Using PET or PET/CT: Systematic Review and Meta-analysis

OBJECTIVE

To evaluate the diagnostic accuracy of positron emission tomography (PET) and PET/computed tomography (CT) for detecting residual and/or recurrent local and regional disease and distant metastases in patients with head and neck squamous cell carcinomas (HNSCCs) following radiotherapy with or without chemotherapy.

DATA SOURCES

A systematic review with no language restrictions was conducted using PREMEDLINE, MEDLINE, EMBASE, and Google Scholar.

REVIEW METHODS

Only prospective studies with histopathological and/or clinical follow-up that assessed the diagnostic accuracy of PET and PET/CT in detecting residual and/or recurrent disease following radiotherapy with or without chemotherapy in patients with HNSCCs were included.

RESULTS

Twenty-seven studies were identified. The pooled sensitivity and specificity of PET and PET/CT for detecting residual or recurrent disease at the primary site was 86.2% and 82.3%, respectively. For residual and recurrent neck disease, the sensitivity and specificity were 72.3% and 88.3%, while for distant metastases, the values were 84.6% and 94.9%.

CONCLUSIONS

PET and PET/CT are highly accurate in detecting residual and/or recurrent HNSCC. PET/CT is more specific than PET alone. Specificity is also greater for scans performed more than 12 weeks after radiotherapy with or without chemotherapy. The authors support the use of PET/CT after 12 weeks posttreatment for the assessment of residual or recurrent disease.

[18F]-FDG PET-CT prediction of response to induction chemotherapy in head and neck squamous cell carcinoma: preliminary findings

OBJECTIVES

The present study assessed the predictive value of [18F]-FDG PET-CT (positron emission tomography with 18-fluoro-eoxyglucose radiotracer, coupled to computerized tomography) for response to induction chemotherapy in head and neck squamous cell carcinoma (HNSCC).

MATERIAL AND METHODS

[18F]-FDG PET-CT was systematically performed before treatment initiation and after the first cycle of chemotherapy. Results were compared with those of endoscopy and pathologic analysis of biopsy and surgical specimens.

RESULTS

This preliminary study included 21 previously untreated HNSCC patients. A decrease of more than 30% in SUVmax (maximum standard uptake value) during induction was predictive of tumor response to chemotherapy (P=0.04). PET-CT measurement of hypermetabolic volume based on a predetermined SUV threshold (SUV=2.5), on the other hand, proved non-predictive.

CONCLUSION

These preliminary findings are promising. A larger sample, however, would be required in order to determine a more precise SUVmax reduction cut-off threshold during induction. Other methods for determining metabolic volume thresholds will be investigated. If functional imaging proves contributive, it could enable early screening of non-responders, avoiding unnecessary intoxication.

Diagnosis of Bilateral Tonsil Cancers via Staging PET/CT: Case Report and Review

Diagnostic workup of metastatic head and neck squamous cell carcinoma of unknown primary site has traditionally included CT and/or MRI imaging and endoscopic biopsies. Routine bilateral tonsillectomy is highly controversial and the role of PET/CT is evolving, both for identification of potential primary sites and the detection of distant metastases. We report a case of cervical nodal metastasis of squamous cell carcinoma from an unknown primary site, in which dual-modality PET/CT led to the unexpected diagnosis of synchronous bilateral tonsillar cancers. In addition, PET/CT correctly distinguished pulmonary sarcoidosis from metastatic disease in this patient.

Clinical Applications of FDG PET and PET/CT in Head and Neck Cancer

18F-FDG PET plays an increasing role in diagnosis and management planning of head and neck cancer. Hybrid PET/CT has promoted the field of molecular imaging in head and neck cancer. This modality is particular relevant in the head and neck region, given the complex anatomy and variable physiologic FDG uptake patterns. The vast majority of 18F-FDG PET and PET/CT applications in head and neck cancer related to head and neck squamous cell carcinoma. Clinical applications of 18F-FDG PET and PET/CT in head and neck cancer include diagnosis of distant metastases, identification of synchronous 2nd primaries, detection of carcinoma of unknown primary and detection of residual or recurrent disease. Emerging applications are precise delineation of the tumor volume for radiation treatment planning, monitoring treatment, and providing prognostic information. The clinical role of 18F-FDG PET/CT in N0 disease is limited which is in line with findings of other imaging modalities. MRI is usually used for T staging with an intense discussion concerning the preferable imaging modality for regional lymph node staging as PET/CT, MRI, and multi-slice spiral CT are all improving rapidly. Is this review, we summarize recent literature on 18F-FDG PET and PET/CT imaging of head and neck cancer.

Combined FDG-PET/CT for the detection of unknown primary tumors: systematic review and meta-analysis

The aim of this study was to systematically review and meta-analyze published data on the diagnostic performance of combined 18F-fluoro-2-deoxyglucose positron emission tomography/computed tomography (FDG-PET/CT) in the detection of primary tumors in patients with cancer of unknown primary (CUP). A systematic search for relevant studies was performed of the PubMed/MEDLINE and Embase databases. Methodological quality of the included studies was assessed. Reported detection rates, sensitivities and specificities were meta-analyzed. Subgroup analyses were performed if results of individual studies were heterogeneous. The 11 included studies, comprising a total sample size of 433 patients with CUP, had moderate methodological quality. Overall primary tumor detection rate, pooled sensitivity and specificity of FDG-PET/CT were 37%, 84% (95% CI 78–88%) and 84% (95% CI 78–89%), respectively. Sensitivity was heterogeneous across studies (P = 0.0001), whereas specificity was homogeneous across studies (P = 0.2114). Completeness of diagnostic workup before FDG-PET/CT, location of metastases of unknown primary, administration of CT contrast agents, type of FDG-PET/CT images evaluated and way of FDG-PET/CT review did not significantly influence diagnostic performance. In conclusion, FDG-PET/CT can be a useful method for unknown primary tumor detection. Future studies are required to prove the assumed advantage of FDG-PET/CT over FDG-PET alone and to further explore causes of heterogeneity.

Role of fluorodeoxyglucose-PET versus fluorodeoxyglucose-PET/computed tomography in detection of unknown primary tumor: a meta-analysis of the literature

The objectives of this study were to evaluate the diagnostic accuracy of fluorodeoxyglucose (FDG)-PET and FDG-PET/computed tomography (CT) in the detection of primary tumors in patients presenting with carcinoma of unknown primary (CUP) unidentified by conventional workup, and to compare the statistical difference between the FDG-PET and FDG-PET/CT. Twenty-eight studies (involving a total of 910 patients) published between 1990 and 2007 were reviewed. These studies evaluated the role of FDG-PET and FDG-PET/CT in the detection of unknown primary tumors after physical examination and conventional workup failed to detect a primary tumor. Systematic methods were used to identify, select, and evaluate the methodological quality of the studies as well as to summarize the overall findings of sensitivity, specificity, and detection capacity of the primary tumor. The overall sensitivity and specificity of FDG-PET in detecting unknown primary tumors were 0.78 [95% confidence interval (CI): 0.72-0.84)] and 0.79 (95% CI: 0.74-0.83), respectively. Furthermore, FDG-PET detected 28.54% of tumors that were not apparent after CUP failed to be detected by conventional workup. Data were collected on the locations of primary tumors detected by FDG-PET in 17 studies and detected by FDG-PET/CT in seven studies. Tumors from the base of the tongue accounted for 20.7% (six of 29) of all false-positive FDG-PET scans, corresponding to a false-positive rate of 28.6% (six of 29), much higher than tumors from the others. FDG-PET exhibited a lower sensitivity with respect to the tumors at the base of the tongue and tonsils, which was 68.2 and 76.7%, respectively. In the eight studies with 430 patients diagnosed with CUP by FDG-PET/CT, 31.4% (n=135) of primary tumors were detected. The pooled sensitivity and specificity were 0.81 (95% CI: 0.74-0.87) and 0.83 (95% CI: 0.78-0.87), respectively. FDG-PET and FDG-PET/CT can detect primary tumors that went undetected by physical examination and conventional workup. FDG-PET exhibited lower sensitivity with respect to the tumors at the base of the tongue and the tonsils.

18-FDG PET in the diagnosis of laterocervical metastases from occult carcinoma

The management of patients with cervical node metastasis (CNM) from carcinoma of unknown primary (CUP) often includes several radiographic studies and invasive procedures that are only successful in detecting an occult primary tumour in less than 25% of the cases. In this prospective study we have assessed the role of total body positron emission tomography (PET) using an 18-F-fluorodesoxyglucose (FDG) in the detection of primary tumours in patients with metastases from CUP. Thirteen patients with lymph node metastases from cytologically verified CUP have undergone total body FDG PET which confirmed the possibility of lymph nodal lesion; all patients have also undergone conventional imaging with CT and/or MRI. The data obtained with the FDG-PET method have subsequently been confirmed both by the histopathological examination and by the clinical course of the disease. The current work aims at assessing and defining the effectiveness of the FDG-PET method during the diagnostic work-up of laterocervical metastasis from CUP conventionally examined with CT and/or MRI; based on our results, we recommend a flow-chart for the clinical-diagnostic management of the patient affected by laterocervical metastasis in the absence of known primary.

Interpretability of PET/CT imaging in head and neck cancer patients following composite mandibular resection and osteocutaneous free flap reconstruction

BACKGROUND

We investigated positron emission tomography (PET)/CT scanning following segmental resections and osteocutaneous free-flap reconstruction. The interpretability of PET/CT imaging with healing osteotomies and reconstruction hardware was analyzed.

METHODS

Patient scans within 18 months of surgery were interpreted for malignancy. Interpretations were compared with clinical data to determine sensitivity/specificity. Standardized uptake values (SUVs) were determined for bony controls, osteotomies, and tumors and were analyzed using paired t test.

RESULTS

Fifteen scans were visually interpreted, 13 underwent SUV analysis. Reconstruction hardware did not interfere with interpretability. Sensitivity and specificity were 88% and 86%, respectively. Osteotomy sites averaged 25% higher SUVs compared with bony controls (vs sternum p = .003, vs mandible p = .008). Tumor SUVs were higher than osteotomies (p = .023) and controls (vs sternum p = .013, vs mandible p = .025).

CONCLUSION

Although osteotomies were characterized by an increased fluorodeoxyglucose signal, scan interpretability was unimpaired. Our study suggests that PET/CT imaging can be utilized to survey free-flap patients at acceptable levels of sensitivity/specificity.

[Positron emission tomography in head and neck squamous cell carcinomas]

18F-Fluorodeoxyglucose positron emission tomography (PET) is an imaging modality which is becoming increasingly esential in oncology, especially in the management of head and neck squamous cell carcinomas (SCC). The most common uses of the PET are listed in this thematic study: initial staging, cervical lymph node metastases from an unknown primary tumor and post-therapeutic follow-up. The advantages and drawbacks of this imaging tool are exposed here according to both our experience and data from the literature. Decision schemes are suggested for each use so as to optimize the use of this imaging modality in the management of these SCC. Other fields of application for the PET are mentioned, such as the in-progress evaluation of response to chemotherapy, the interest of this imaging tool in radiotherapy as well as current biochemical developments concerning new tracers.